Field of the Invention
The present invention relates to an organic light emitting diode display device, and more particularly, to an organic light emitting diode display device capable of improving reliability.
Discussion of the Related Art
Image display devices for displaying various image information have become increasingly slim, lightweight, and portable in keeping with consumer demand in the information age. An organic light emitting diode display device that displays an image by controlling the amount of light of an organic emission layer is spotlighted as a flat panel display device capable of reducing weight and volume of a cathode ray tube (CRT).
An organic light emitting diode display device includes a thin film transistor and an organic light emitting diode connected to the thin film transistor formed in each sub pixel region of a substrate. Since the organic light emitting diode is vulnerable to moisture and oxygen, an encapsulation substrate is formed to cover the organic light emitting diode.
The organic light emitting diode includes a first electrode constituting an anode, an emission layer (EML) and a second electrode constituting a cathode which are sequentially formed. When a voltage is applied between the first and second electrodes, holes and electrons are recombined in the EML to generate excitons. Light emission occurs via transition of excitons from an excited state to the ground state.
In particular, a flexible organic light emitting diode display device may be implemented by forming an organic light emitting diode on a flexible substrate and forming an encapsulation substrate using a flexible cover film. In this case, however, the cover film has a different coefficient of thermal expansion from a bottom film attached to the lower surface of the flexible substrate in order to prevent moisture or oxygen from infiltrating through the flexible substrate. Accordingly, the organic light emitting diode display device may warp, thereby deteriorating reliability.
Furthermore, the bottom film and an optically clear adhesive (OCA) generally used to attach the bottom film to the flexible substrate have poor resistance to humidity. Thus, reliability of the organic light emitting diode display device against moisture is deteriorated.